14a: Swine Repro

Why would outdoor swine ops have higher litter mortality

Piglets can’t regulate their body temperature

Virus that drove a lot of the biosecurity changes in the swine industry in the 90’s

PRRSV

Average number of litters per sow in effective operations

2.5/year

How does a sow operation determine productivity

Number of pigs weaned per sow per year

Type of cyclicity in the sow

Non-seasonal polyestrus

When might sows and boars experience seasonal infertility and why

Summer; heat

When do gilts reach puberty

7 mos

Primary factors that influence onset of puberty in gilts

Plane of nutrition and exposure to boars during maturation

Average cycle length in sows

20.5 days

Average estrus length in sows

48-72 hours

Average estrus length in gilts

36-48 hours

How long does it take a sow to ovulate

2 hours

When should you AI gilts

12 and 24 hours after onset of estrus

What should you AI sows

24 and 36 hours after onset of estrus

Signs of estrus in sows

• Fence walking by boars

• Vulvar swelling ± mucus

• Grunting

• Sawhorse stance when you apply back pressure (standing heat)

Artificial ways to detect heat in sows

Sprays that mimic boar pheromones

How does suckling inhibit estrus

Suckling → endorphins → increased prolactin → decreased insulin and decreased LH

Characteristics to evaluate when deciding on replacement gilts

• Conformation

• Shoulders

• Hips

• Number of teats

When should you expose a replacement gilts to a boar

6 mos

Best way to synchronize sows in a large operation

Wean everyone together

Minimum length that a piglet should be on a sow if you plan to synchronize with weaning

3 weeks

How long after weaning will a sow come into estrus

4-7 days

Medication we can use to induce estrus in show gilts

PG 600

Drugs in PG 600

eCG and hCG

Crude, outdated protocol to sync sows

Breed, abort with prostaglandin, and rebreed when she comes into heat in 4-7 days

How long does it take for a CL to mature in the sow

12 days

What happens if your show gilt doesn’t respond to PG 600

She has already reached puberty

If your show gilt has already hit puberty, how can you synchronize/induce estrus

Use prostaglandins >12 days after heat

Oral medication that can be used to synchronize sows

Altrenogest (liquid progesterone)

Types of prostaglandin drugs

• Dinoprost (lutalyse): natural

• Cloprostenol (estrumate): synthetic

Why do you need to be careful when giving prostaglandins to pigs

It has systemic effects due to uterine vasculature

Why is prostaglandin not always an effective product for estrus synchronization

You need to know when she was last in heat to know if the CL is mature enough to respond

When would we use GnRH to synchronize sows

Post weaning

Nutrition change key post breeding

Cut down feed intake and protein for 72 hours post breeding so progesterone is not suppressed

What is required for oxytocin to work

E₂

How do we use hormones to increase litter size during breeding

GnRH given at first breeding, oxytocin given 5-10 minutes after first breeding and after second breeding

How do many large operations determine if a gilt/sow is pregnant

Non-return rate int he presence of a boar

Drawback of laymen using ultrasound for pregnancy detection in sows

The lay machines may detect the bladder and call it pregnancy

Proper location to scan with a lay ultrasound for pregnancy detection in sows

Paramedian to the mammary

General mechanism behind MRP in the sow

Pulls PGF₂a out of circulation to prevent luteolysis